Vapour barrier in a detached concrete garage?

[Hsmith192]

Hi everyone, I already have my roof insulated and I put my heater on two days ago and could get to about 14.5/ 15 degrees which was nice, however I’m noticing my humidity meter was reading between 80-90%.

How do I get this percentage down? Is it by using a vapour barrier with wall and floor insulation?

 

[eribaMotters]

Concrete structures are seldom a warm place to work in. Insulation and vapour barriers are a good idea, but you will need some air flow to limit any potential condensation.
You have insulated the roof, but I'm guessing your concrete floor may be the cause of the moisture levels as it will not have a dpc, even though it could have a water-proofer in the mix.
Several things, what type of heater are you using as if burning gas or this may be causing the moisture levels. Also consider that as temperatures rise then so do humidity levels as warm air can carry more moisture.

Colin

 

[Jameshow]

Concrete structures are seldom a warm place to work in. Insulation and vapour barriers are a good idea, but you will need some air flow to limit any potential condensation.
You have insulated the roof, but I'm guessing your concrete floor may be the cause of the moisture levels as it will not have a dpc, even though it could have a water-proofer in the mix.
Several things, what type of heater are you using as if burning gas or this may be causing the moisture levels. Also consider that as temperatures rise then so do humidity levels as warm air can carry more moisture.

Colin

Agreed without a dpm and vapour barrier (even osb or celotex will do) you won't get the moisture down tbh.

 

[Hsmith192]

Hi what’s the difference between a damp proof membrane and a vapour barrier? I’m using a 2500w fan heater.

Just brought some wickes vapour barrier and hopefully that will help! I’m going to need to put 50mm PIR on the walls too I guess.

Thank you again guys.

 

[Jameshow]

Dpm is a heavy plastic membrane.

But a vapour barrier can be much lighter plastic or the foil of pir, or possibly the glue of osb / plywood (I'd paint it on the outside face)

 

[Bob008]

Hi everyone, I already have my roof insulated and I put my heater on two days ago and could get to about 14.5/ 15 degrees which was nice, however I’m noticing my humidity meter was reading between 80-90%.

How do I get this percentage down? Is it by using a vapour barrier with wall and floor insulation?

Best solution for the floor is use 1200gauge visqueen dpm covered with 20mm ridged pir insulation taped at the joints then some decent 18mm plywood (but a cheap set of t&g cutters for the router Amazon ) leave the visqueen 400mm longer at the edges then overlap more visqueen behind it and up the walls then cover the walls with 50mm pir ridged insulation this method works as I’ve done it in my damp workshop and it’s stopped 90% of the damp cast iron surfaces aren’t affected anymore and it’s a good solution

 

[Bob008]

Best solution for the floor is use 1200gauge visqueen dpm covered with 20mm ridged pir insulation taped at the joints then some decent 18mm plywood (but a cheap set of t&g cutters for the router Amazon ) leave the visqueen 400mm longer at the edges then overlap more visqueen behind it and up the walls then cover the walls with 50mm pir ridged insulation this method works as I’ve done it in my damp workshop and it’s stopped 90% of the damp cast iron surfaces aren’t affected anymore

 

[phat bob]

I have a sectional concrete garage I put visqueen on the concrete then 2x2 and chipboard also built 2x2 walls fastening visqueen on the back insulated and boarded the front after 10 minutes with my heater on I have to turn it off and after 10 years it's all still going well

 

[Lard]

Just for further info....lDPMs and VBs stop any form of moisture (from water down to vapour) from passing through.
Breather membranes are somewhat the opposite in that they allow vapour, but not water, to pass through - thus allowing you, together with a combination of ventilation, to control the amount of vapour in the air.
I've seen people confuse the two by stating that VB are (incorrectly) breather membranes.

 

[Jameshow]

Just for further info....lDPMs and VBs stop any form of moisture (from water down to vapour) from passing through.
Breather membranes are somewhat the opposite in that they allow vapour, but not water, to pass through - thus allowing you, together with a combination of ventilation, to control the amount of vapour in the air.
I've seen people confuse the two by stating that VB are (incorrectly) breather membranes.

Dpm and VB are like boil in the bag jackets.

Breather membranes are like goretex and let's moisture out but not water in...

 

[Hsmith192]

Thanks everyone, I’ve gone with this product for the walls but might need the same again or something “thicker” or different for the floor as it feels a tad cooler than the walls.

 

[HOJ]

something “thicker” or different for the floor

With floors you need to use a 1200 Gauge DPM, as @Bob008 has already mentioned, walls/ceilings only need a 500 gauge vapour barrier.

 

[Hsmith192]

Excellent I’ve got the walls sorted then, just need to get the floor sorted now- thanks again everyone.

 

[TomGW]

Hi what’s the difference between a damp proof membrane and a vapour barrier? ......

A dpm is intended to prevent moisture getting into the structure from outside, commonly in the floor. On the other hand a vapour barrier is intended to prevent moisture entering the structure from within the building, from the moist air generated by the activities of the occupants - cooking, showering, breathing etc.

 

[Hsmith192]

A dpm is intended to prevent moisture getting into the structure from outside, commonly in the floor. On the other hand a vapour barrier is intended to prevent moisture entering the structure from within the building, from the moist air generated by the activities of the occupants - cooking, showering, breathing etc.

Sounds silly but how do I know where the moisture/damp air is coming from? If you cover with DPM and VP do you just mask the problem or make it worse?